The present invention relates to a data communication device for a vehicle towed by a motor vehicle, to which electrical energy is transmitted by a cable connection from the motor vehicle. The invention also relates further to a method of using this type of data communication device.
Commercial towed vehicles (including semitrailers) usually obtain their electrical power for signal lamps, lights, electrical control circuits, including an anti-lock braking system (ABS) from the motor vehicles towing them. This has the consequence that the electronic and/or electrical operating units in the towed vehicle or trailer do not function when the connection to the towing vehicle is broken. An anti-lock braking system (ABS) has been prescribed for commercial trailers and semitrailers for some time. In an ABS system wheel sensors detected motion of the wheels and input suitable pulses to a central ABS controller. The operation of the brakes is controlled by pneumatic values so that the locking of the brakes is prevented. A plug of the trailer must be connected to a standard socket of the vehicle for switching of the ABS system, so that the controller obtains electrical power. An error signal is transmitted by the connection, which signals whether the ABS system is error-free or a self-testing device contained in the ABS system detects operating errors. Newly developed anti-lock braking system have an expanded control function, in which additional data such as pneumatic shock absorber data, various error data and electronic mileage meter data can be integrated. Moreover a coating wear monitor for the brakes can be performed and the appropriate data can be stored. The output of this data usually occurs manually using a diagnostic connection and requires a manual documentation or by a connectable moveable terminal to which the data can be transmitted.
There is a considerable need to reliably determine the distance covered by the towed vehicle. The electronic mileage determined by counting wheel pulses from the ABS system fails, when the driver circumvents the operating circuit of the ABS system by manual operations, disconnects the ABS connection and interrupts the current flow from the towing vehicle to the ABS. In this situation, of course, the ABS is no longer operative, but the standard pneumatic operating brakes do continue to operate.
It is known further to equip the trailer with a mechanical mileage meter on the wheel hub. However these devices are prone to interference during rough operation and further are easily manipulated or adjusted.